Xylitol is a commercially available polyol with unique health benefits. It is traditionally produced from the reduction of xylose isolated from xylose-rich biopolymers, as in U.S. Pat. Nos. 2,989,569, 3,558,725, and 4,008,285. As these process are resource and cost intensive, researchers have sought for novel methods for the production of xylitol. These include various synthetic chemical processes, the use of microorganisms, and processes such as fermentation. As the structure of xylitol is similar to that of glucose, one can produce xylitol-precursors by decarboxylating carbon-6 of glucose. D-Glucuronic acid (glucose with carbon-6 oxidized to a carboxylic acid) and its derivatives are ideal candidates for such a decarboxylation. Heikkila et al., in published US patent application US2003/0097029, describes the production of xylitol from sources including glucuronic acid. However, in every case where D-glucuronic acid is used as the starting material, it is first hydrogenated to yield L-gulonic acid, which is then decarboxylated by either hypochlorous acid (Example 5) or by the Ruff Degradation (Example 6), both standard carbohydrate decarboxylation methods, to yield L-xylose. Despite these developments, there remains a need to produce xylitol in a manner that is low cost and yields high-purity product.
Stapley et al., in published US patent application US2005/0272961, describe a novel electrolytic oxidative decarboxylation technique using the otherwise decarboxylation-resistant D-glucuronic acid or D-glucuronic acid glycoside as a substrate to yield xylo-pent-1,5-diose, which is easily hydrogenated to xylitol. However, to realize the commercial viability of the electrolytic decarboxylation of D-glucuronic acid or D-glucuronic acid glycoside, there remains a need for an anode which converts D-glucuronic acid or D-glucuronic acid glycoside to yield xylo-pent-1,5-diose with a desirably high current efficiency and high reaction selectivity. Therefore, there remains a need for improved methods and electrodes for performing the electrolytic oxidative decarboxylation of glucuronoside substrates with improved current efficiency and/or reaction selectivity.